New perylene polyimides containing p‐n diblocks for sensitization in TiO2 solar cells

Three novel perylene polyimides (PPIs) containing p‐n diblock units were designed and synthesized for use in dye‐sensitized mesoporous TiO₂ solar cells. They all dissolve in m‐cresol and N‐methyl‐2‐pyrrolidone (NMP). Their visible light absorption, electrochemical and photoelectrochemical properties were systematically studied. The polyimides have band gap energies of 2.16, 2.19 and 2.25 eV deduced from ultraviolet–visible absorption spectra, and electron affinity (E_a) and ionization potential (IP) of ?3.93 and 6.10 eV for PPI1, ?3.94 and 6.13 eV for PPI2, ?3.93 and 6.59 eV for PPI3, respectively, deduced from cyclic voltammogram. Experimental data show that introduction of 4,4′‐bisaminetriphenylamine cannot only greatly enhance optic‐electro conversion efficiency, but also enhance the dissolubility which in favorable for making the devices. The relationship of structure and properties of PPI is discussed and the mechanism of photocurrent generation is explained. Copyright © 2004 John Wiley & Sons, Ltd.     

Diffusion-induced Spatio-temporal Oscillations in an Epidemic Model with Two Delays

We investigate a diffusive, stage-structured epidemic model with the maturation delay and freelymoving delay. Choosing delays and diffusive rates as bifurcation parameters, the only possible way to destabilize the endemic equilibrium is through Hopf bifurcation. The normal forms of Hopf bifurcations on the center manifold are calculated, and explicit formulae determining the criticality of bifurcations are derived. There are two different kinds of stable oscillations near the first bifurcation: ...     

锗钨酸分子间化合物的合成和结构研究

以锗钨酸和4-甲基吡啶为原料合成了分子间化合物H₄GeW₁₂O₄₀·5C₆H₇N·CH₃CN。单晶X-射线分析表明，属正交晶系，空间群P2₁2₁2₁, 晶胞参数a=13.533(5),b=20.835(5), c=21.859(7)?，V=6164(3)?³。Dc=3.650 Mg/m³, Z=4。对3934个可观察到的衍射点进行全矩阵最小二乘法修正后，可靠性因子R=0.0534。     

Synthesis, crystal structure and characterization of a 2-D network organic-inorganic hybrid polymer with [α-BW12O40]5- as building blocks

A two-dimensional network compound [Ce(DMF)4(H2O)][α-BW12O40]·H2O·(HDMA)2 (HDMA = protoned dimethylamine, DMF = N,N-dimethylformamide) was synthesized from α-H5BW12O40·nH2O, Ce(NO3)3·6H2O and DMF and characterized by IR, UV spectra and TG-DTA. The result of the X-ray single crystal diffraction indicates that the crystal is monoclinic, space group P21/n, with unit cell dimensional: a = 1.1983(3), b = 2.4216(5), c = 1.9517(4) nm, β = 92.91(3)°, Z = 4, R1 = 0.07710, wR2 = 0.1416. Structural analysis indicates that every [Ce(DMF)4(H2O)]3-building block is surrounded by three adjacent [α-BW12O40]5-polyanions, meanwhile, every [α-BW12O40]5-polyanion interconnects with three neighboring [Ce(DMF)4(H2O)]3+ subunits, by making use of which two-dimensional network structure can be constructed. The result of thermogravimetric analysis manifests that the title compound has two-stage weight loss and the decomposition temperature of the title polyanionic framework is 560℃. The electrochemical analysis shows the title polyanion has three-step redox processes in the pH = 4-7 media.     

流动注射分光光度法测定水体总磷

提出了一种单通道紫外消解流动注射比色分析法，能快速测定水样中总磷。实验采用了微量恒流混合泵、新型的细长型高灵敏度流通池及紫外消解器、液流分配阀、恒流瓶等FIA装置，并使用工业编程控制器和智能触摸屏进行控制和计算，使操作更为方便。此法分析时间短，测量范围宽，精度高，适合于各种水体的测定。     

Self-repairing polymers: poly(dioxaborolane)s containing trigonal planar boron

The molecular weight of poly(dioxaborolane)s can be controlled during the polymerization reaction or through post-polymerization processing in such a manner that hydrolytic damage to these materials may be repaired, thereby regenerating the polymer.